1. Field
The present application relates generally to wireless communications, and more specifically to methods and systems for using multiple handover metrics as a handover trigger for inter-frequency handovers.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, wideband code division multiple access (WCDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system.
Further, in some WCDMA FDD multi-carrier (multi frequency) scenarios, inter-frequency handover based on user equipment (UE) event triggered measurement reports using either a received signal code power (RSCP) metric only or an energy per chip divided by a interference spectral density (Ec/No) metric only thresholds for the target frequency may not be optimal. For example, currently, 3GPP specifications define events 2b and 2c with only one type of target frequency quality threshold (RSCP or Ec/No). As such, under the current standard, a network may configure consecutive event 2b's or one event 2b followed by an event 2c to determine whether the target frequency quality fulfills multiple thresholds. As such, there is an increased the risk of call drops due to fast degrading radio frequencies (RFs), delays associated with a radio network controller (RNC) sending a second event configuration message, or delays associated with transmitting a response to a second event configuration message.
Thus, improved apparatus and methods for facilitating efficient handover are desired.